A U.S. Navy coastal patrol ship fired warning shots at an Iranian naval vessel that was approaching it in an unsafe manner, U.S. Central Command (CENTCOM) said Tuesday.

The Iranian ship approached within 150 yards of the USS Thunderbolt (PC-12), a Cyclone-class patrol ship during coalition exercises in the Persian Gulf. CENTCOM said the Iranian vessel did not respond to repeated attempts to establish radio communication as it approached.

An Inranian IRGCN vessel (left) makes a close approach to the USS Thunderbolt coastal patrol ship (right) in the Persian Gulf on July 25, 2017. Photo: U.S. Navy.
An Inranian IRGCN vessel (left) makes a close approach to the USS Thunderbolt coastal patrol ship (right) in the Persian Gulf on July 25, 2017. Photo: U.S. Navy.

The Navy called the Iranian ship’s actions as “unsafe and unprofessional interaction” occurring in international waters.

When the vessel did not respond to communication, the Thunderbolt fired warning flares and sounded an internationally-recognized danger signal consisting of five short blasts on the ship whistle. Navy officials said the Iranian ship continued approaching anyway and the Thunderbolt crew again fired the warning blasts before firing warning shots in front of the vessel.

The Navy said after that the Iranian vessel halted its approach. The Navy said the Iran ship’s actions were not in accordance with internationally known “rules of the road” or recognized maritime customs. This created a risk of collision, CENTCOM said.

The Thunderbolt was conducting the exercise with two Coast Guard cutters, an Army logistics ship, and the USS Vella Gulf (CG-72) Ticonderoga-class guided missile cruiser.

In a video first obtained by USNI News a watch stander refers to the Iranian ship as an Iranian Revolutionary Guard Corps Navy (IRGCN) vessel. The IRGC is separate from the rest of Iran’s military, and directly reports to the country’s leadership.

The IRGC claimed in a statement released to the state-run Fars News Agency that the U.S. ship was sailing towards the IRGCN patrol ship. The IRGCN said it “was patrolling in international waters, and fired two shots into the air with the aim of provocation and intimidation.”

The IRGCN frequently conducts provocative actions against U.S. and allied naval vessels in the Persian Gulf. In June an Iranian vessel trained a laser on a U.S. helicopter accompanying a group of Navy ships transiting the Strait of Hormuz, in March an IRGCN patrol boat stopped short in front of the USNS Invincible (T-AGM-24), and in January the USS Mahan (DDG-72) fired three warning shots to ward off several IRGCN approaching it and other U.S. Navy ships transiting the strait.

The Thunderbolt is one of 10 PCs forward deployed to Manama, Bahrain and is assigned to Task Force 55. Forward based PCs conduct maritime security operations (MSO) in the northern Persian Gulf to protect Iraqi oil terminals and sea-based infrastructure as well as other counter-terrorism operations.

PC ships are armed with two MK38 chain guns, two Mk19 automatic grenade launchers, and two .50 caliber machine guns.